The present invention relates to a removable adhesive sheet or tape which is excellent in removability, more particularly to a removable adhesive sheet or tape which is excellent in removability even after frequent repetition of bonding to and removal from an adherend, and does not permit adhesive fine particles to remain on the surface of the adherend.
There are known removable adhesive tapes or sheets using adhesive fine particles as a constituent element. However, in those conventional removable adhesive tapes, there is a problem that fine particles which are adhesive components remain on an adherend when bonded to and removed from the adherend. This problem becomes more remarkable when the adherend is a diazo copying paper.
There is a removable adhesive tape in which a binder is used in an amount of approximately 1/2 to 1/5 as much as the weight of adhesive fine particles to adhere the fine particles onto a substrate, for the purpose of resolving the problem as described above [see, for example, West German Patent No. 24 17 312 (corresponding to U.S. Pat. No. 3,857,731) and Japanese Unexamined Published Utility Model Application Nos. 60661/1979 and 42881/1980].
However, even when a binder is used as described above, adhesion or fixation of fine particles on a substrate is still not sufficient, and when an abrupt removal is effected, there still exists a problem that fine particles remain on an adherend.
Further, there has been proposed a method in which a pressure sensitive adhesive (hereinafter referred to as an adhesive) such as an acrylic emulsion type adhesive, etc., is used as a binder in order to adhere or attach fine particles more securely on a substrate (see U.S. Pat. No. 3,857,731).
However, in this method, a new problem has been raised that, in addition to insufficient attachment of fine particles onto a substrate, not only the fine particles but also the adhesive used as a binder remain on an adherend. Further, in this method, there is a fear that the so-called picking would be generated.
Also there has been known an invention in which adhesive fine particles having a shape which is approximately semi-spherical are attached onto a primer resin layer provided on a substrate without any use of a binder (see Japanese Examined Published Utility Model Application No. 57394/1982).
However, in this invention, the fine particles are limited to ones having an approximately semi-spherical shape, and also it is essential that these fine particles are attached to a substrate in such a state that the curved surface thereof is necessarily positioned at the outer side, i.e., the substrate and the fine particles are brought into contact with each other so as to make the contact area therebetween to be larger.